chore(skills): pr-review — point reviewers at team worktree, not main

Sprint 37 PR #138 review produced 6 false-positive findings because
the reviewer defaulted to Read/Grep on the main repo path instead of
the sprint-37/copy branch worktree. Every finding was a verbatim match
against main's state but irrelevant to the branch — the branch had
already cleaned the residue being flagged as "still present." False
negatives are the same drift running the other direction: bugs
introduced on the branch never get seen because the reviewer never
reads the branch.

Fix: resolve the team worktree path before spawning reviewers
($(dirname <repo>)/.sprint/sprint-N/<team>/) and pass it into the
reviewer prompt with non-negotiable language. The worktree IS the
branch; Read/Grep on paths rooted there cannot resolve to main.

Fallback (no worktree — e.g. non-sprint branch or post-teardown):
git show origin/<branch>:<path>. Explicitly flagged in the prompt
so the reviewer knows Read/Grep on any local path is wrong.

.claude/skills/pr-review/SKILL.md

@@ -138,24 +138,57 @@ Three-dot diff with pathspec exclusions is unreliable. Instead, either:
 For large diffs (>1000 lines of source), provide **source files** rather than
 raw diff to reviewers — cleaner context, better reviews.
 
-**Reviewer agents read source files via `git show`.**  Sprint branches
-use the naming pattern `sprint-{N}/{team}`. To read a file from the
-branch being reviewed:
+**Reviewer agents read source files from the team worktree.**
+
+Sprint branches follow `sprint-{N}/{team}`. Mid-sprint, a worktree
+of each branch exists at `$(dirname <repo_root>)/.sprint/sprint-{N}/{team}/`
+— a *sibling* of the repo root, not a child. This worktree IS the
+branch: Read/Grep on paths rooted there resolve against the branch's
+checkout, not main's.
+
+**Why this matters:** Sprint 37 PR #138 review produced 6 false-
+positive findings because the reviewer defaulted to Read/Grep on the
+main repo path (`/var/mnt/data/projects/settled-reach/main/`) instead
+of the branch worktree. Every finding was a verbatim match against
+main's state but irrelevant to the branch — the branch had already
+cleaned the residue the reviewer flagged as "still present." Sending
+those findings to the team would have caused busywork on already-clean
+code, and more dangerously, the same drift hides *false negatives*
+(branch-introduced bugs the reviewer never saw because it never read
+the branch).
+
+Fix: before spawning reviewers, resolve the worktree path and pass it
+into every reviewer prompt with prominent language. The reviewer
+reads from the worktree, not from main.
 
 ```bash
-git show origin/<branch>:<path>
+# Determine worktree path
+SPRINT_NUM=$(echo "<branch>" | sed -E 's|sprint-([0-9]+)/.*|\1|')
+TEAM=$(echo "<branch>" | sed -E 's|sprint-[0-9]+/||')
+REPO_ROOT=$(git rev-parse --show-toplevel)
+WORKTREE="$(dirname "$REPO_ROOT")/.sprint/sprint-${SPRINT_NUM}/${TEAM}"
+
+# Verify it exists and matches the branch tip
+git -C "$WORKTREE" rev-parse HEAD   # should equal `git rev-parse origin/<branch>`
 ```
 
-For example:
-```bash
-git show origin/sprint-31/server:server/src/bin/atlas.rs
-```
+If the worktree exists and its HEAD matches `origin/<branch>`, use it
+as the reviewer's source of truth. If it doesn't exist (e.g. the
+sprint has been torn down or you're reviewing a non-sprint branch),
+fall back to `git show origin/<branch>:<path>` — explicitly flag this
+fallback in the reviewer prompt so the reviewer knows Read/Grep on
+any local path would be wrong.
 
-If the sprint branch has an active worktree (under `.sprint/`), reviewers
-can also use the Read tool with the worktree path. But `git show` is
-the reliable default — it works whether or not a worktree exists.
+In the reviewer prompt, state the rule non-negotiably:
 
-Also tell agents to read relevant `decisions/*.md` files for context.
+> **Read source from `<WORKTREE_PATH>` only.** Do NOT Read or Grep
+> paths under the main repo root (`/var/mnt/data/projects/settled-reach/main/`).
+> Those resolve to main, not the branch. The worktree at `<WORKTREE_PATH>`
+> IS the branch — point all file tools there.
+
+Also tell agents to read relevant `decisions/*.md` files for context
+(these can be read from either path — they're usually identical —
+but for consistency, use the worktree path).
 
 ### 4. Spawn reviewers in parallel